Swiss snowboarding champion Estelle Balet was killed in an avalanche on Tuesday after a slab of snow broke away during a film shoot in Switzerland and swept her down a narrow, rocky slope.

Police say the 21-year-old Swiss athlete was struck early on Tuesday morning while filming above Orsieres, near Switzerland’s southern border with France and Italy. She had been following another snowboarder, who wasn’t caught in the avalanche.

Valais state police said in a statement that rescuers were able to free Balet, who had been wearing special safety equipment, but she died at the scene.

Balet recently won the Freeride World Tour. She was a member of watchmaker Swatch’s professional team. Freeride snowboarding takes place away from prepared routes and athletes are often at more risk of being caught in avalanches due to riding off piste.

Police say they have launched an investigation into the cause of the incident. “Despite immediate efforts to revive her, she died at the scene,” police said. “An investigation has been started to determine the causes of the accident.”